To provide a damper for a building capable of utilizing an interior space of the building by reducing a size of the damper for the building in a horizontal direction and narrowing an area where the damper occupies in the interior space of the building.

A damper for a building which has two columns arranged at an interval includes: a first member which is fixed to one of the two columns and extended from the one of the two columns in a horizontal direction; a second member which is arranged between the one of the two columns and the other of the two columns and has a first position where the second member is attached to the first member so as to be rotatable around a rotation axis of the same, a second position at a distance in an upward direction from the first position and a third position at a distance in a horizontal direction from the first position; a third member which connects the second position and the other of the two columns; a fourth member which is fixed to the one of the two columns at the interval in a downward direction from the third member; and a hydraulic or an air pressure cylinder with an upper end section and a lower section thereof attached to the third position and the fourth member respectively.